Owing to the tautomeric instability of vinylamine, poly(vinylamine) (pVA) and vinylamine copolymers are made indirectly by (co)polymerization of a derivative of vinylamine, such as N-vinylformamide, and subsequent removal of the derivatizing group. Previous methods for conversion of poly(N-vinylformamide) (pNVF) or analogous polymeric intermediates to pVA entail hydrolysis with either strong base (U.S. Pat. No. 4,393,174) or acid (U.S. Pat. No. 4,808,683). Japan Kokai Tokkyo Koho, Jp 61 118406 (1984) discloses the preparation of pVA by treatment of pNVF with a mixture of aqueous ammonia or alkylamine at room temperature, followed by hydrolysis with aqueous sodium or potassium hydroxide.
U.S. Pat. No. 4,421,602 discloses the production of copoly(N-vinylformamidevinylamine) by reaction of pNVF with acid or base. Aqueous sodium or potassium hydroxides are preferred and the use of ammonia or amines is disclosed, but not exemplified. In the latter instance, removal of formamide groups as the corresponding monomeric formamides is indicated. In each case, inorganic coproducts are formed in conjunction with pVA; base hydrolysis leads to alkali metal salts of the derivatizing group (eg, sodium or potassium formate), while acid hydrolysis gives the corresponding salt of pVA and formic acid. Neutralization provides pVA, accompanied by a salt of the acid used for hydrolysis and (unless formic acid was removed) a formate salt. Although some applications of pVA are insensitive to the presence of inorganics, many, including those in adhesives and coatings, require essentially salt-free pVA. Separation of these coproducts from pVA has been accomplished by traditional routes such as precipitation, selective extraction, or ultrafiltration. In all instances, however, preparation of salt-free pVA entails tedious removal and disposal of stoichiometric quantities of an inorganic coproduct.
Similar hydrolytic procedures have also been used to generate amine functional copolymers from the corresponding NVF copolymers. However, partial conversion of any additional hydrolytically labile functionality in the copolymer is often observed. Thus, hydrolysis of copolymers of NVF with (meth)acrylamides (U.S. Pat. No. 4,808,683), (meth)acrylonitrile (U.S. Pat. Nos. 4,957,977 and 5,064,909), or (meth)acrylates (U.S. Pat. No. 5,037,927) under acidic conditions yields amine functional polymers which also contain carboxylate groups. U.S. Pat. No. 4,921,621 reports comparable results with basic hydrolyses of NVF-acrylamide copolymers. U.S. Pat. No. 5,281,340 discloses amidine-containing polymers which are the products of acidic hydrolysis of NVF-(meth)acrylamide copolymers. U.S. Pat. No. 4,774,285 discloses water soluble polymers which are obtained by hydrolysis of copolymers of NVF with a variety of comonomers, eg, vinyl esters, N-vinylpyrrolidinone, (meth)acrylates, under strongly acidic or basic conditions. Copolymerized vinyl esters are also hydrolyzed, especially under basic conditions.
U.S. Pat. No. 4,943,676 discloses the thermolysis of pNVF as a route to pVA. High temperatures (&gt;200.degree. C.) are required, conversions to pVA are low to moderate, and difficultly soluble, crosslinked products are obtained. While the last disadvantage may be overcome by inclusion of water, the resulting products still contain formate salts.
H. M. Colquhoun, et al, "Carbonylation", Plenum Press, New York, 1991, pp 207-225 report transition metal-mediated decarbonylations, especially of aromatic substrates. Aromatic aldehydes are decarbonylated catalytically by treatment with Pd/C at high temperature (the boiling point of the aldehyde, typically &gt;200.degree. C.). Poor selectivities are often obtained, owing to functional group sensitivity under the reaction conditions. Stoichiometric decarbonylations of aromatic aldehydes have been done with "Wilkinson's catalyst" [chlorotris(triphenylphosphine)rhodium] under mild conditions; however, the starting rhodium complex must be regenerated in a separate step. Cationic rhodium complexes of bridging diphosphines may be used for catalytic decarbonylation of aromatic aldehydes. The latter catalysts are extremely sensitive, and are active only under rigorously anhydrous and anaerobic conditions. Attempted extension of both stoichiometric and catalytic decarbonylations to aliphatic aldehydes is further complicated by multiple reaction pathways and extensive byproduct formation via .beta.-elimination and/or isomerization of organometallic intermediates. Attempted decarbonylations of carboxylic acid derivatives have met with less success. Treatment of aroyl chlorides with stoichiometric quantities of "Wilkinson's catalyst" yields arylrhodium complexes; (chloro)arenes are not formed at temperatures &lt;200.degree. C. Catalytic decarbonylation of aroyl halides has been accomplished with this complex under forcing conditions (200.degree.-300.degree. C.); selectivity to desired products may again be an issue. Poor selectivity is encountered with aliphatic acid chlorides as the result of .beta.-elimination and/or isomerization. Consequently, although catalytic carbonylation of monomeric amines to produce formamides and/or ureas has been demonstrated, the reverse process is virtually unknown.
Palladium(II) chloride-catalyzed decarbonylation of monomeric formamides is mentioned qualitatively and very briefly in a monograph "Organic Synthesis via Metal Carbonyls" ed. I. Wender and P. Pino, Wiley-Interscience, New York, Vol. 2, 1977, p. 630; however, no further detail has appeared in the literature. S. Kotachi, et al, Catal. Lett., 19, 339-334 (1933) observed decarbonylation of formanilide as a competing pathway in the production of carbamates from alcohols and formanilide with homogeneous ruthenium catalysts. Catalytic decarbonylation of pNVF or NVF copolymers, however, has not been reported in either the journal or patent literature.